Function CopyToString

common/values/string_value.h:319–321

  std::string ToString() const { return value_.ToString(); }

  void CopyToString(std::string* absl_nonnull out) const {
    value_.CopyToString(out);
  }

  void AppendToString(std::string* absl_nonnull out) const {
    value_.AppendToString(out);